OOP in C simple example

#include <stdio.h>
#include <stdlib.h>
typedef struct base base_t;
typedef struct child child_t;
typedef struct base{
    int (*getId)(void* self);
    void (*free)(void* self);
    int id;
} base_t;
int getId(void* self){
    return ((base_t*)self)->id;
}
void base_free(void* bse){base_t* bs = (base_t*)bse; free(bs);}
base_t * base_new(){
    base_t *res = malloc(sizeof(base_t));
    res->getId = getId;
    res->free = base_free;
    return res;
}
typedef struct child{
    int (*getId)(void* self);
    void (*free)(void* self);
    base_t *super;
    char name[10];
} child_t;

int getChildId(void* self){
    return ((child_t*)self)->super->id;
}

void child_free(void* bse){
    child_t* chld = (child_t*)bse;
    chld->super->free(chld->super);
    free(chld);
}

child_t* child_new(){
    child_t* chld = malloc(sizeof(child_t));
    chld->super = base_new();
    chld->getId = getChildId;
    chld->free = child_free;
    return chld;
}

int main(int argc, char **argv){
    base_t *bse = base_new();
    bse->id = 0;
    child_t *child;
    child = child_new();
    child->name[0] = '1';
    child->super->id = 1;
    int n = 2;
    void* mass[2] = {bse, child};
    for (int i=0; i<n; i++){
        int id = ((base_t*)mass[i])->getId(mass[i]);
        printf("id =%i\n", id);
    }
    child->free(child);
    bse->free(bse);
    return 0;
}